The Federation observation outpost on planet Cestus III is destroyed which leads the USS Enterprise to make first contact with the Gorn, who are responsible for the outpost's destruction as well as the deaths of two Enterprise crewmen, because the Gorn claim the outpost was in their territory. The Enterprise also makes first contact with the Metrons, who become impressed with Humanity when Captain James T. Kirk shows mercy and spares the life of a Gorn captain after the Metrons set up an arena-style conflict between the two of them. (TOS: "Arena")

The USS Enterprise uncovers the truth behind the disappearance of the starship Archon that had been lost a hundred years earlier, when it visited the planet Beta III. The Enterprise is responsible for the destruction of the computer known as Landru which had ruled Beta III as a despot for 6,000 years. The ship leaves behind its sociologist Lindstrom and a team of specialist to restore that planet's culture to a more Human form. (TOS: "The Return of the Archons")